Everything has a shelf life, even gasoline, diesel, and kerosene (yes, people still use kerosene). In fact, when you store gas and diesel-powered equipment, you have to use additives to help the gas/diesel along through its storage time. All these fuel sources expire eventually but does propane go bad?
Propane puts the rest to shame because it’s not only a dominant source of fuel but it doesn’t go bad. It has no expiration date and there is no shelf life that can be applied to it. Propane tanks, on the other hand, are where the expiration problems lie.
The tanks that hold propane expire 12 years from the date that that propane was first bottled in a brand new one. Recertified tanks often have a shorter expiration date, between 5 and 10 years, with the occasional 12 years if the tank is recertified a certain way.
In Canada, propane tanks don’t even get the luxury of a 12-year bottle. They bottle and certify theirs for up to 10 years maximum with their certification and recertification procedures largely the same as in the US.
How to know the age of your propane tank
It’s easy to lose track of how old your propane tank is, especially if it ends up on a shelf in the shop for a few years and you’ve practically forgotten all about it. Fortunately, even if your propane tank has rusted up pretty good, which is a common problem, the dates you need to know are marked into the metal.
You will usually find the tank manufacturing and expiration date on the metal ring around the nozzle on the top. It may not always be a metal ring, but its usually set in a series of handles at the top of the propane tank.
These metal stamps contain the tank’s manufacturing date, the expiration date, and the tank’s origination. If its pretty rusty, you can usually sand it down and see the dates, as they are stamped deeply into the metal. The dates are in the month-day format.
For instance, if your tank’s origin date was January of 2012 and the expiration date is January of 2024, then the dates will be represented as “01-12” and “01-24”. Even though 2024 is still two years away, its always advisable to have your tanks recertified every 10 years, rather than waiting until the last minute.
You should never find any of the dates that you need on the body of the tank, because stamping something like that into the metal would weaken the integrity of the tank, which will most likely spend the majority of its life with a lot of pressure coming from within.
Additional markings on a propane tank
Propane tanks come with several informative markings, not including the dates. The information is useful when it comes time to refill and/or recertify the propane tank.
- TW: Tare Weight
- WC: Water Capacity
- A, B, C, and D: Quarterly dates
- 08 21: Indicates the expiration date
The tar weight is important because it helps you determine how much propane you have left in your tank, in pounds. Tare weight is the weight of an object on its own, completely empty. For instance, weighing a glass cup, before you fill it with water, will give you the “tare” weight of the glass cup.
All you need to determine how many pounds of propane you have left in the tank, is weight the tank in pounds and subtract the tare weight from the total weight. The alphabet is not trying to teach you your A B Cs, but merely indicates the quarter of the year in which the tank was manufactures and needs to be recertified.
The water capacity number is the amount of water that the propane tank will hold, despite the fact that you’re not going to be filling your tank with water. Its a number that’s used when the tank is recertified and during a refill.
The water capacity number is also used to ascertain the total volume of propane in the tank. Propane is interesting both in its gaseous form and in its liquid state. As the temperature around propane increases, the propane volume also increases.
This is why propane tanks are never filled to 100% capacity. In fact, there is an “overfilling prevention device” inside the propane tank that keeps you from being able to fill the tank above 80%.
Propane volume decreases when the temperatures decrease. It also becomes harder to for the propane to reach the burner because as it shrinks in the cold, the pressure in the tank decreases. A decrease in pressure makes it difficult to push the propane up and out, which is necessary for it to touch the air and turn into a gaseous state that can be burned.
For this reason, the general rule of thumb is to keep your propane tank at least 30% full, so that it always has enough pressure—even in colder temperatures—to properly distribute at the nozzle and to your burner so you can cook or warm yourself up.
Why using propane in an expired tank is dangerous
According to the Consumer Product Safety Commission (CPSC), 600 propane tanks start fires or explode every year. Propane tanks aren’t exactly coddled after they are manufactured.
Propane tanks are used for grilling, shop work, construction jobs, shipbuilding, and as fuel sources for a number of industrial vehicles, like fork lifts. As they are transported to store shelves, they are knocked around, dropped, and generally mishandled all of the time.
Before your new propane tank is used at home, its been dragged, tossed into the back of the truck, fallen over on its side, had other metal objects or heavy duty materials shoved up against it, and so much more.
That’s where the problem lies because over time, propane tanks take quite a beating. The 12-year recertification date is actually quite generous, consideiring what the tank probably goes through in its life time.
The tank may be compromised and you would never realize it without having it recertified. Working or grilling with a compromised propane tank is exceedingly dangerous and, along with the potential for slow leaks, is a major reason for getting your tank recertified.
How to check your propane levels on your own
You don’t ever have to worry about your propane expiring but sometimes its good to know how much you have left, especially if you’re planning a large get-together and your’re going to be grilling out.
- Use hot water to determine fill level by feel
- Use the tare weight method
- Use math and timing
- Purchase one of three gauge types
Hot water method
This is an old school method that works nicely, even if it doesn’t give you a precise number to determine the exact volume. People that use propane all of the time don’t really need precise numbers and could tell you at any given point in time how much is left.
For those using propane for the first time and don’t have a gauge, the hot water method will give you an invisible line that the propane is sitting at inside the tank. Pour hot water over the tank, allowing it to run down the side.
When you’re done pouring, run your hand slowly down the side of the tank, starting from the top, when you hit the cold line, that’s where your propane is.
The tare weight method
Discussed above, the tare weight method is as simple as weighing the propane tank and subtracting the weight of the tank from the number. The tare weight is listed on the side of the tank and, after you subtract it, you’ll know how many pounds of propane you have left.
Math and timing method
A single gallon of propane produce 92,000BTUs of energy. Your burner or grill will have a BTUH (BTUs per hour) number on it or in the user manual. Divide 92,000 BTUs by the BTUH of your grill to get the time it will take to burn a gallon of propane on your grill’s highest setting.
Purchase one of three gauge types
There are three types of gauges that you can use with your propane tank:
- Analog Propane Scales
- Digital Propane Scales
- Inline Propane Pressure Gauges
The analog and digital weight scales use the tare weight method to keep track of the pounds of propane remaining in the tank. The digital version measures constantly while the analog requires you to lift and weigh the tank.
The inline pressure gauge sits between the burner and the cut off valve of the propane tank. It measures your remaining propane by determining the pressure remaining, which decreases as propan volume decreases.
While the propane inside your propane tank has an indefinite shelf life, the tank itself does not. Keep track of the dates on your propane tank and be sure to get them recertified at the ten year mark.
Of course, ten years is a long time and, if you have a lot of propane tanks, difficult to keep up with. Make a habit of double checking the date each time you pull one out to fire up the burner and you’ll always be on point.